This invention relates to a process for making o-aryl benzonitrile by reacting o-chlorobenzonitrile (OCBN) with a substituted phenylmagnesium halide. In particular, it relates to a method of making o-tolylbenzonitrile (OTBN) by reacting OCBN with p-tolylmagnesium chloride in the presence of a nickel catalyst, an ethereal solvent, and N-methylpyrrolidinone (NMP) as a cosolvent.
OTBN is a key intermediate for the synthesis of antihypertensive drugs. Various methods have been reported in the literature for making OTBN. As described in patents DE 19607135, JP 08109143, and EP 566468, OTBN can be made by reacting o-bromobenzonitrile (OBBN) with p-tolylmagnesium bromide in the presence of a Pd, Ni, or Mn catalyst. While those processes produce OTBN with a good yield, the starting materials (both OBBN and p-bromotoluene) are very expensive. In JP 08231454, OCBN is reacted with p-tolylmagnesium chloride in the presence of a zinc salt and an amine to give OTBN.